math.complex: fix handling of the argument to the log() method, replace tests (#25863)

Author: tankf33der

vlib/math/complex/complex.v

@@ -138,7 +138,7 @@ pub fn (c Complex) ln() Complex {
 // Based on
 // http://www.milefoot.com/math/complex/summaryops.htm
 pub fn (c Complex) log(base Complex) Complex {
-	return base.ln().divide(c.ln())
+	return c.ln().divide(base.ln())
 }
 
 // Complex Argument

vlib/math/complex/complex_test.v

@@ -292,25 +292,11 @@ fn test_complex_arg() {
 }
 
 fn test_complex_log() {
-	// Tests were also verified on Wolfram Alpha
-	mut c1 := cmplx.complex(5, 7)
-	mut b1 := cmplx.complex(-6, -2)
-	mut c2 := cmplx.complex(0.232873, -1.413175)
-	mut result := c1.log(b1)
-	// Some issue with precision comparison in f64 using == operator hence serializing to string
-	assert result.str() == c2.str()
-	c1 = cmplx.complex(-3, 4)
-	b1 = cmplx.complex(3, -1)
-	c2 = cmplx.complex(0.152198, -0.409312)
-	result = c1.log(b1)
-	// Some issue with precision comparison in f64 using == operator hence serializing to string
-	assert result.str() == c2.str()
-	c1 = cmplx.complex(-1, -2)
-	b1 = cmplx.complex(0, 9)
-	c2 = cmplx.complex(-0.298243, 1.197981)
-	result = c1.log(b1)
-	// Some issue with precision comparison in f64 using == operator hence serializing to string
-	assert result.str() == c2.str()
+	a := cmplx.complex(11.22, 33.44)
+	b := cmplx.complex(55.66, 77.88)
+	c := a.log(b)
+	assert c.re.eq_epsilon(0.8032210844549097)
+	assert c.im.eq_epsilon(0.10605953671930149)
 }
 
 fn test_complex_cpow() {